Prior art adjustable open ended wrenches typically incorporate a thumb wheel or similar mechanism to adjust the jaw opening size of the wrench so as to snugly grasp a faceted head of a workpiece, such as a fastener. A snug grip is important to maximize the contact surface area between the jaws and the workpiece thereby avoiding damage, principally resulting from slippage and point contact deformation, to the fastener as torque is applied to a workpiece. The typical adjustable open ended wrench maintains a fixed jaw opening size once adjusted to fit the fastener. As the fastener is rotated, the user must reposition the tool so as to restore a convenient position of the tool handle to once again apply torque. The repositioning action requires a user to lift or slide the jaw opening away from the workpiece disengaging the tool from the workpiece, repositioning, and reengaging the tool with the workpiece. The disadvantage of lifting and repositioning of the tool is well recognized and the inconvenience is typically sacrificed in favor of the convenience of the adjustable open ended features for particular applications requiring side access to a fastener or minimizing the need for stowing multiple fixed sized sockets or wrenches. Ratcheting wrenches provide a mechanism to rotate the fastener without removing the wrench from the fastener and typically incorporate a jaw or socket mechanism that surrounds the fastener head requiring approaching the fastener from above. Consequently a user must make an election as to the type of wrench to use in a particular application and must also provide multiple variations of the tools thereby expanding tool kit required so as to be prepared for a wide variety of applications.
Numerous attempts have been pursued to improve the performance of adjustable open ended wrenches principally directed to providing some form of ratcheting wherein the tool need not be disengaged or removed from the workpiece for repositioning the tool handle after each torquing stroke. One such attempt is illustrated by Brown in U.S. Pat. No. 6,889,579 wherein a cam action is taught to position a series of jaw elements movable radially from the workpiece so as to selectably clamp on to a hex fastener for rotation of the workpiece during the torque stroke and released during repositioning; however, the jaw mechanism is not open ended, the jaw size range is limited, and no ratcheting mechanism is provided.
Other prior art attempts incorporate a quasi ratcheting mechanism wherein an element of the tool provides for a small motion of a jaw element either selectably by an operator activated lever mechanism or by an incorporated element in the tool activated by the action of rotating the engaged tool in a particular direction. True ratcheting mechanisms remain fully engaged with a workpiece at all times during torque application and rotational repositioning of the tool handle. Typical quasi ratcheting mechanisms have a disadvantage in that the workpiece can be firmly gripped often resulting in slippage and damage to the fastener.
Janson, in U.S. Pat. No. 5,941,142, teaches a wrench having a quasi ratcheting function wherein the handle is rotated backwards to reset the handle for a torque stroke in 60 degree increments without removing the tool from the workpiece or loosening the fastener. True ratchets can be reset in much smaller increments. Brown wrenches employ the typical method of adjusting the open ended jaw opening size by turning a worm gear that operates on a rack attached to the movable jaws. Quasi ratcheting is typically accomplished by incorporating a movable element within one jaw face allowing the tool to clamp against a workpiece in the torque stroke direction and releasing the workpiece in the reverse free return stroke direction wherein the jaw faces slip to the next facet of the workpiece. The span of movement of the movable element is typically small thus a resizing of the jaw openings requires manual adjustment of the opening to accommodate other workpiece sizes. Alternatively, a movable element is incorporated to provide small movement of one jaw of the tool away from the workpiece thusly effectuating a similar ratcheting action as. These prior art quasi ratcheting mechanisms, despite being an incremental improvement over traditional adjustable wrenches, are slow to adjust as the size range accommodated by the movable portion of the jaw face is typically small there by necessitating adjustment of the worm gear. Also prior art quasi ratcheting mechanisms generally do not clamp firmly onto a workpiece in part because the surface contact area on the workpiece is small due to larger tolerances resulting from the loose fit. A firm grip of the tool onto a workpiece is essential to prevent damage to a workpiece during the torque stroke.
What is needed is a wrench combining the advantageous features of an adjustable open ended wrench facilitating a variety of access approaches to a workpiece and minimizing the number of tools of varying jaw size, while also providing a ratcheting mechanism; and, a simple and rapid jaw opening size change mechanism having a firm clamping action to eliminate clearances and to prevent damage to fasteners thereby improving the utility of the tool and overcoming disadvantages of the prior art.